Both rats and humans acquire strong taste aversions (TAs) when ingetibles are paired with gastrointestinal distress. Many alcoholics develop strong aversions when alcohol-related stimuli are repeatedly paired with emmetically- or verbally-induced nausea. However, many others fail to condition. The value of TA alcoholism treatments would be enhanced by criteria for identification of TA prone and resistant alcoholics. This project is developing strains of rats that are TA prone (TAP) or TA resistant (TAR) through selective breeding based on cyclophosphamide-induced TAs to a saccharin solution. The goal is the development of animal phenotypes suitable for analyses of physiological bases of individual differences in conditionability. Selective breeding for TA learning efficiency has produced marked strain divergence over eleven selected generations. TA strain separation is a robust conditioning phenomena that extends to rotationally induced (motion-sickness) saccharin aversions, and has also been maintained with conditioned stimulus (CS) flavors other than saccharin, the CS basis of strain selection. Due both to basic interest in physiological substraits of different types of learning, and to applied concerns about the use of biologically appropriate aversion therapies, shock-motivated environmental avoidance (SMEA) is also being studied, but is not a factor in strain selection. TA strain separation has not resulted in comparable changes in SMEA learning. Continued development and maintenance of these unique strains should produce animals that will be of considerable interest and value to scientists from various disciplines. Selective breeding and study of SMEA will continue. Pica and activity studies will be used to assess TAP and TAR sickness reactivity to cyclophosphamide and rotation. TA induction via LiCl, alcohol and amphetamine will also be studied. Results will provide direction for additional studies of commonality of diversity of mechanisms of TA induction via different interventions. This project is expected to generate future proposals to study possible endocrine and putative neurotransmitter bases of TA proneness. Long term results are likely to facilitate selection of aversion prone alcoholics, and may eventually facilitate TA alcoholism treatments through clinically effective pharmacological enhancement of conditionability.